A brush seal is a commonly used device for sealing between a rotating component, such as a shaft, and an adjacent stationary surface. The brush seal includes one or more arrays of brushes that are generally radial in orientation and extend between the rotating surface and the stationary surface. Each array of brushes is sandwiched between a backing plate and a side plate. The backing plate is on the lower pressure side and extends nearly the length of the brushes to prevent the bristles of the brushes from bending away from the high pressure side.
The bristles are typically angled slightly relative to the radial direction and away from the direction of rotation. This feature prevents buckling of the bristles during use and reduces wear. Another source of wear results from the rotation of the seal induced by contact with the rotating surface.
Reverse installation of the annular brush seals is also a contributor to wear and improper functioning of the seal. If installed backwards, the backing plate is on the high pressure side and therefore provides no support to prevent bending of the bristles into the low pressure side. This bending reduces the effectiveness of the sealing contact between the brush seal and the rotating surface. Further, the bristles will be angled into the direction of rotation and, as a result, buckling of the bristles will be encouraged rather than discouraged. This also contributes to reducing the effectiveness of the seal. In addition, the brush seal may not seat properly if installed backwards, which may lead to higher levels of vibration and increase the risk of damage to the seal.
Prior art devices to prevent reverse installation include provision of a pin that is received by an opening machined into the side plate of the brush seal but not the backing plate. Another prior art device includes a lip machined into the side plate that cooperates with a groove machined into the support structure. Brush seals are typically made by sandwiching the bristles between the side plate and the backing plate and then welding the sandwiched apparatus together. After bonding, the assembled brush seal is machined to form the opening or lip that is needed to prevent reverse installation.
A recent example of a brush seal assembly that prevents reverse installation is described in U.S. Pat. No. 5,066,025, issued to Hanrahan and entitled "Brush Seal Assembly". In this device, a recess is machined into the support structure that defines the carrier for the brush seal. The recess is sized to accept the shorter side plate but not the longer backing plate. Reverse installation will offset the axial position of the seal such that a retaining ring cannot be installed. Therefore, reverse installation is precluded without requiring special machining of the brush seal.
The above art notwithstanding, scientists and engineers under the direction of Applicants' Assignee are working to develop improved brush seals.